Python wrapper for the C implementation of the Generic Sensor Format library.
- Free software: MIT license
- Notes on licensing: The bundled
gsfpy3_0x/libgsf/libgsf03_0x.sobinaries are covered by the LGPL v2.1 license. Copies of this license are included in the project atgsfpy3_0x/libgsf/libgsf_LICENSE.md. The top-level MIT licensing of the overallgsfpyproject is not affected by this. However, as required by the libgsf license, the libgsf shared object libraries used by thegsfpy3_0xpackages at runtime may be replaced with a different version by setting theGSFPY3_08_LIBGSF_PATHand/orGSFPY3_09_LIBGSF_PATHenvironment variables to the absolute file path of the new library.
The gsfpy package provides three namespaces: gsfpy, gsfpy3_08 and gsfpy3_09.
The default version of GSF supported is 3.08. Top level package functionality for 3.08 can be used either via import gsfpy (without setting the DEFAULT_GSF_VERSION environment variable - see below) or import gsfpy3_08. Note that import gsfpy will also work for versions 3.06 and 3.07 of GSF as well (older versions have not been tested).
If you are using GSF v3.09, there are two options:
- Set the
DEFAULT_GSF_VERSIONenvironment variable to"3.09", thenimport gsfpy - Import the 3.09 package directly with
import gsfpy3_09
-
The
gsfpy(3_0x).bindingsmodules provide wrappers for all GSFlib functions, including I/O, utility and info functions. Minor exceptions are noted in the sections below. -
For added convenience the gsfpy top level package provides the following higher level abstractions:
open_gsf()GsfFile(class)GsfFile.read()GsfFile.get_number_records()GsfFile.seek()GsfFile.write()GsfFile.close()
pip install gsfpypip install git+ssh://[email protected]/UKHO/gsfpy.git@masterpip install git+https://github.com/UKHO/gsfpy.git@masterfrom ctypes import string_at
from gsfpy3_08 import open_gsf
from gsfpy3_08.enums import RecordType
with open_gsf("path/to/file.gsf") as gsf_file:
# Note - file is closed automatically upon exiting 'with' block
_, record = gsf_file.read(RecordType.GSF_RECORD_COMMENT)
# Note use of ctypes.string_at() to access POINTER(c_char) contents of
# c_gsfComment.comment field.
print(string_at(record.comment.comment))from ctypes import c_int, create_string_buffer
from gsfpy3_09 import open_gsf
from gsfpy3_09.enums import FileMode, RecordType
from gsfpy3_09.gsfRecords import c_gsfRecords
comment = b"My comment"
# Initialize the contents of the record that will be written.
# Note use of ctypes.create_string_buffer() to set POINTER(c_char) contents.
record = c_gsfRecords()
record.comment.comment_time.tvsec = c_int(1000)
record.comment.comment_length = c_int(len(comment))
record.comment.comment = create_string_buffer(comment)
with open_gsf("path/to/file.gsf", mode=FileMode.GSF_CREATE) as gsf_file:
gsf_file.write(record, RecordType.GSF_RECORD_COMMENT)from ctypes import byref, c_int, pointer
from gsfpy import *
# This example uses the bindings module to illustrate use of the lower level functions
file_handle = c_int(0)
data_id = gsfDataID.c_gsfDataID()
source_records = gsfRecords.c_gsfRecords()
target_records = gsfRecords.c_gsfRecords()
ret_val_open = bindings.gsfOpen(
b"path/to/file.gsf", enums.FileMode.GSF_READONLY, byref(file_handle)
)
# Note use of ctypes.byref() as a shorthand way of passing POINTER parameters to
# the underlying foreign function call. ctypes.pointer() may also be used.
bytes_read = gsfpy.bindings.gsfRead(
file_handle,
enums.RecordType.GSF_RECORD_COMMENT,
byref(data_id),
byref(source_records),
)
# Note use of pointer() rather than byref() when passing parameters to
# gsfCopyRecords(). Implementation of this function is in Python as calling
# the native underlying function causes memory ownership clashes. byref()
# is only suitable for passing parameters to foreign function calls (see
# ctypes docs).
ret_val_cpy = bindings.gsfCopyRecords(
pointer(target_records), pointer(source_records)
)
ret_val_close = bindings.gsfClose(file_handle)from gsfpy3_09.bindings import gsfIntError, gsfStringError
# The gsfIntError() and gsfStringError() functions are useful for
# diagnostics. They return an error code and corresponding error
# message, respectively.
retValIntError = gsfIntError()
retValStringError = gsfStringError()
print(retValIntError, retValStringError)The gsfPrintError() method of GSFlib is not implemented as there is no
FILE* equivalent in Python. Use gsfStringError() instead - this will
give the same error message, which can then be written to file as
required.
gsfFree() the sibling method to gsfCopyRecord() in GSFlib, used to
deallocate memory assigned by the library but managed by the calling
application, is not required by gsfpy as memory allocation and
deallocation is handled by ctypes. gsfFree() is therefore omitted from
the package.
Implementation of the GSFlib function
gsf_register_progress_callback() is not applicable for gsfpy as the
DISPLAY_SPINNER macro was not defined during compilation. It is
therefore omitted from the package.
Generic Sensor Format specification: see e.g. https://github.com/schwehr/generic-sensor-format/blob/master/doc/GSF_lib_03-06.pdf
Generic Sensor Format C library v3.06 specification: see e.g. https://github.com/schwehr/generic-sensor-format/blob/master/doc/GSF_spec_03-06.pdf
More recent versions of these documents can be downloaded from the Leidos website.
Ensure Poetry is installed before proceeding
By default Poetry will create it's own virtual environment using your system's Python. This feature can be disabled.
git clone [email protected]:UKHO/gsfpy.git
cd gsfpy
poetry installA good choice if you want to run a version of Python different than available through your system's package manager
git clone [email protected]:UKHO/gsfpy.git
cd gsfpy
pyenv install 3.8.3
pyenv virtualenv 3.8.3 gsfpy
pyenv local gsfpy
poetry installmake testmake lintSome known concerns relating to the underlying GSFlib C library are documented at dwcaress/MB-System#368 and https://github.com/schwehr/generic-sensor-format/issues. Note that gsfpy simply wraps GSFlib and does not purport to stop or mitigate these potential vulnerabilities. It is left to the authors of applications calling gsfpy to assess these risks and mitigate where deemed necessary.
GSF data processed using gsfpy should be sourced from reliable providers and checked for integrity where possible.
Please also refer to the LICENSE file for the terms of use of gsfpy.
libgsf03-08.so was built from the
Leidos C code using the
Makefile in UKHO/libgsf
This package was created with Cookiecutter and the UKHO/cookiecutter-pypackage project template.
Also see schwehr/generic-sensor-format
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